Post navigation

When to use vancomycin

The most common use for vancomycin is in invasive Gram positive infections

You need to consider

Infection site

Patient weight

Kidney function

Pathogen susceptibility

Pharmacokinetics

Vancomycin has bad oral bioavailability so it’s almost never used as a pill

Occasionally it is orally to supplement C. diff infections (because that’s going on in the GI tract)

Volume of distribution: IV serum 0.4-1 L / kg

Normally vancomycin doesn’t cross the blood brain barrier very well, but in the setting of meningitis the inflamed meninges increases permeability

Adverse effects

Redman syndrome: A histamine-like flushing during or immediately after dose. Occurs mostly on the face and neck. This is NOT life threatening

Treatment: anti-histamine, pause infusion, then restart at a slower rate

If the reaction is severe, stop the infusion, give antihistamines, wait until symptoms resolve before restarting. When you restart, give the infusion reaaaalllllly slooooooowly (over more than 4 hours)

Nephrotoxicity

Dosing

This is where vancomycin can get tricky, because you are aiming for a target trough (between dose) serum concentrations.

Generally the target is 10 mcg/ml, but this may need to be higher for treating MRSA or osteomyelitis

Trough concentrations should be measured 30 minutes before the 4th dose any time a course of vanco is started or the dose is changed

Monitor creatinine at least once a week (remember that whole nephrotoxicity bit)

Starting dose should be 15-20 mg/kg (based on actualnot ideal body weight) every 12 hours. This usually works out to 1-2 g IV Q12H. If the kidneys are not working well, reduce the dose.

Renal replacement therapy (RRT) is a process of removing waste products and excess free water from the blood during renal failure and critical illness.

Common indications for RRT can be remembered with the mnemonic AEIOU:

(Metabolic) Acidosis

Electrolyte abnormalities (especially severe hyperkalemia)

Ingestions/toxins (aspirin, lithium, methanol, ethylene glycol)

(Volume) Overload

Uremia

There are many different variations of RRT, but the main principles behind it can be quite simple.

In hemodialysis, diffusion is responsible for removing unwanted solutes and water. The setup involves a semipermeable membrane that can allow water and some water-soluble molecules to pass. Blood will flow on one side of the membrane, under pressure, while the dialysate (contains glucose and some electrolytes) generally flows on the other side in the opposite direction. This creates a suitable concentration gradient for unwanted molecules to pass into the dialysate, while excess water is forced across the membrane based on the amount of pressure is applied by the dialysis circuit.

In hemofiltration, blood is pushed across a semipermeable membrane, under pressure. Most of the plasma water is able to pass through the membrane, while unwanted molecules get stuck in the membrane (convection). A substitution fluid may be added back to the blood, in order to dilute out waste molecules (e.g., urea), replace useful molecules (e.g., bicarbonate), and to avoid losing too much fluid from the patient’s circulation.

Some modes of RRT will involve both hemodialysis and hemofiltration. Others only use one of these mechanisms.

Tumescent solution is also called “Klein’s Solution” after the physician who characterized the recipe and the use of it.

It’s called “tumescent” because it makes things tumescent, which is a fancy word for swollen. Tumescent is a dilute solution of lidocaine, epinephrine, and sodium bicarbonate that is injected in the subcutaneous tissue (fat). The epinephrine is the most important ingredient as it causes vasoconstriction, this means that the blood loss that could be a big problem for large procedures like burn surgery and liposuction becomes much less of a big deal.

The other interesting thing is that since fat is relatively avascular compared to other tissues, the “safe amount” of tumescent is much higher than what is normally stated for injections of lidocaine or epinephrine.

For example, it was reported by Klein that the toxic dose of lidocaine for tumescent solution is 35 mg/kg of body weight.

There are a few different recipes for tumescent anesthesia, the one presented in the doodle is the one first outlined by Klein, some use more or less lidocaine or epinephrine.

The carpal bone ossify aka turn into bone aka magically become visible on an x-ray in a predictable order.

The easiest way to remember is that it starts at the capitate (smack dab in the middle) and then goes in a ulnarly-directed spiral. I was going to say “clockwise” or “counter-clockwise” but that would depend on which side of which hand you were looking at. So capitate, followed by hamate and then down to triquetrum and so on. Except for the pisiform, being a sesamoid bone it gets left behind and only develops years later.

Capitate: 1-3 months

Hamate: 2-4 months

Distal radius: 1 year

Triquetrum: 2-3 years

Lunate: 2-4 years

Scaphoid: 4-6 years

Trapezium: 4-6 years

Trapezoid: 4-6 years

Distal ulna: 5-6 years

Pisiform: 8-12 years

I included the distal radius and distal ulna in there for good measure.

I know I could have been fancier with changing the length of the metacarpals or their growth plates, but it was more fun to make the animated gif.

Use the same hand as the patient’s affected hand (suspicious of a right scaphoid problem? Use your right hand to test)

Place your hand on the patient’s so that your thumb is over the volar surface of the scaphoid tubercle (the distal pole). Don’t apply any pressure (remember this area is probably at least a little sore and you want to remain friends for now)

Gently move the wrist through ulnar/radial deviation (you can be fancy and consider this your Watson Test) and flexion/extension to relax the patient

With the patient’s wrist in neutral extension and neutral (or slight radial deviation), forcefully and quickly push the scaphoid tubercle in the dorsal direction

For being such a small anatomic location, people find it very difficult to describe where on the hand or digits things are actually happening when there is an injury.

I think part of it stems back to medical school when we are taught that the digits all have numbers, the thumb is D1, index D2 and so forth. The problem comes when people say “the 3rd finger” and all of the sudden one has no idea whether they are talking about the long finger (D3) or the ring finger (D4 but then, the thumb doesn’t count as a finger, does it?)

Which finger (digit?!) is which?

This is why it’s always best to call digits by their names, this even goes for metacarpals. It is totally OK, and generally less confusing to call a bone the index finger metacarpal.

Thumb = D1

Index = D2

Long = D3

Ring = D4

Small = D5

Which side of the hand?

The same goes for which side of the hand the problem is on. There is no lateral or medial side to the hand. One could argue that it’s how someone is in anatomical position, so obviously the small finger side is medial, unfortunately very few people walk around in anatomic position and it’s their thumbs that point to the body.

So best to describe side by two things that stay put regardless of how someone has their hands in space: the radius and the ulna.

Thumb side = RADIAL

Small finger side = ULNAR

Finally for the top and bottom (or is it back and front) of the hands: use the terms DORSAL (where the nails are) and VOLAR (or palmar)

Amyotrophic Lateral Sclerosis (ALS) is a degenerative disease of the motor neurons in the brain and spinal cord. It progressively affects all the muscles in the body but there is no known cause and no treatment. Only about 5-10% of cases are inherited while the rest are sporadic.

The neurons ALS affects are primarily the upper motor neurons. These are the ones that originate in the brain and travel down the spinal cord. These neurons then synapse with the lower motor neurons in the ventral horn, and it is the lower motor neurons that go directly to the muscles.

In ALS there are both upper motor neuron and lower motor neuron symptoms. As the neurons die, a constellation of symptoms including numbness, weakness and paralysis emerge. Eventually the paralysis progresses leading to inability to speak, swallow and breath. There is no cure for ALS and treatments only help with the symptoms, they do not slow the progression of the disease.

And in case you get tired or jaded seeing your social media full of these videos, watch this one of my father doing it. He’s not an emotional guy, but he has lost more than his fair share of friends to this disease.

Scaphoid fractures are very common but due to its weird blood supply, the scaphoid is prone to not healing well (review the anatomy of the scaphoid in this doodle). This is why fractures of the scaphoid and even SUSPECTED fractures of the scaphoid are treated very conservatively.

Even if you’re suspicious of a fracture but don’t see one on x-ray, that’s enough to subject someone to a cast for 2 weeks and then bring them back to re-x-ray.

This doodle goes through the basic algorithm for treating scaphoid fractures centred around a timeline to show how long the treatment course can be. There are of course nuances to the management, so take a person’s work and hobbies and handedness into consideration. Also, don’t be afraid to consult your friendly hand/wrist specialist.

The scaphoid is the most commonly fractured carpal bone, accounting for almost 70% of fractures. It tends to be young males who break their scaphoid this is both an anatomical thing: younger kids get ligament injuries and older folks break their distal radius and a lifestyle thing: falling on outstretched hands (skateboarding, snowboarding) or throwing a punch both place a lot of force across the scaphoid leading to fractures.

The bad thing about scaphoid fractures is that the blood supply (from a branch of the radial artery) comes from distal to proximal. Since most fractures happen at the waist of the scaphoid the likelihood of having poor blood supply to the fracture site is quite high. It doesn’t help matters that around 80% of the scaphoid is articular surface (joint surface), so if it doesn’t heel well, it can lead to problems with arthritis of the wrist later on.

Presentation

Scaphoid fractures present with a pretty classic story and the person is usually swollen and bruised and will have tenderness in their “snuffbox.” So even if the x-ray doesn’t show a fracture, it’s best to treat with a cast for comfort and safety and then recheck them in 2 week’s time (this will be discussed in a separate post).